1. Field of the Invention
This invention concerns compounds having a plurality of aryl substituted pyridine groups and their use as components of fluorescent chelate labels for fluoroassay techniques.
2. Background Art
Fluoroassay techniques are finding increasing application in chemical, biochemical and medical analyses. Fluorescence measurement methods are intrinsically extremely sensitive. However, the sensitivity of fluorescence assays, in practice, is limited by the presence of background fluorescence.
U.S. Pat. Nos. 4,150,295 and 4,058,732; issued on Apr. 17, 1979 and Nov. 15, 1977, respectively, and a chapter appearing at pages 67-80 of Immunofluorescence and Related Staining Techniques, Knapp, et al eds. (1978, Elsevier/North Holland Biomedical Press) disclose the general concept that background fluorescence has a relatively short life and that one can advantageously employ as measured fluorescent species, materials having a longer lived fluorescence. This work further points out that by using an intermittent excitation source and a time-coupled measurement of fluorescence one could essentially avoid or reject the background fluorescence while measuring the desired fluorescence.
Rare earth chelates have been identified by the art as materials having long-lived fluorescence. Such materials include a rare earth metal ion such as terbium or europium chelated by one or more ligands such as amine polyacids (See, U.S. Pat. No. 4,352,751 of Wieder and Wollenberg), "heteroatom-containing groups" including iminodiacetate substituted phenols, coumarins and phenanthrolines (See, Eastman Kodak European Patent Application 0068875) and aromatic diketones (See, German OLS 2,628,158), to point out a number of representative disclosures.
The present invention concerns a family of aryl pyridine derivatives which may be incorporated into long-lived fluorescent species with rare earth metals. The individual aryl pyridine units which are incorporated in the present compounds are disclosed in our copending U.S. patent application Ser. No. 712,774 filed Mar. 18, 1985 now U.S. Pat. No. 4,761,481. References to the general class of substituted pyridine derivatives include U.S. Pat. Nos. 4,008,239, 3,970,662 and 3,907,808 as well as Carbeteas and Williams, J. Heterocycl. Chem., 11(5), 819 (1974); Weller and Luellen, Tetrahedron Letters, Vol. 22, No. 44, pp 4381-84 (1981) and Weller, Luellen and Weller J. Org. Chem., 47, 4803-06 (1982). The above-noted European Patent Application 0068875 is also of interest. Another reference of interest is WO/84/04970 which discloses a polymer with multiple units of visualization monomer.